Update to match current reality vis-a-vis source collections and
the 4.6 release. Goaded by the PR cited but the actual changes
are somewhat more in line with my thinking on the subject rather
than the PR author's (I don't think anyone else is even capable of
making their minds think that way).
PR: 40757

Change PKGDIR from pkg/ to . Also fix places where ${PKGDIR} is spelled out
(many of which are ${PKGDIR}/MESSAGE -> ${PKGMESSAGE} type fixes that
shouldn't have been necessary) and the string "/pkg/" appear.